Task notification

1. Task Notifications

2. 9.1 Chapter Introduction and Scope
 Communicating Through Intermediary Objects

3. 9.1 Chapter Introduction and Scope
 Task Notifications—Direct to Task
Communication

4. Scope
 A task’s notification state and notification
value.
 How and when a task notification can be
used in place of a communication object,
such as a semaphore.
 The advantages of using a task
notification in place of a communication
object.

5. 9.2 Task Notifications
Benefits and Limitations
 Performance Benefits of Task Notifications
 Faster
 RAM Footprint Benefits of Task Notifications
 Low RAM usage
 Limitations of Task Notifications
 Sending an event or data to an ISR
 Enabling more than one receiving task
 Buffering multiple data items
 Broadcasting to more than one task
 Waiting in the blocked state for a send to
complete

6. 9.3 Using Task Notifications
 Event API:
 BaseType_t xTaskNotifyGive( TaskHandle_t
xTaskToNotify );
 void vTaskNotifyGiveFromISR(
TaskHandle_t xTaskToNotify,
BaseType_t
*pxHigherPriorityTaskWoken);
 uint32_t ulTaskNotifyTake( BaseType_t
xClearCountOnExit,
TickType_t xTicksToWait );

7. 9.3 Using Task Notifications

8. 9.3 Using Task Notifications
 Data API:
 BaseType_t xTaskNotify(
 TaskHandle_t xTaskToNotify,
 uint32_t ulValue,
 eNotifyAction eAction );

 BaseType_t xTaskNotifyFromISR(
 TaskHandle_t xTaskToNotify,
 uint32_t ulValue,
 eNotifyAction eAction,
 BaseType_t *pxHigherPriorityTaskWoken );

9. About “eNotifyAction”
 eNoAction
 Similar to binary semaphore.
 eSetBits
 Use as group event.
 eIncrement
 Used as a binary or counting semaphore, and is
equivalent to xTaskNotifyGive()
 eSetValueWithoutOverwrite
 eSetValueWithOverwrite

10. 9.3 Using Task Notifications
 BaseType_t xTaskNotifyWait
 ( uint32_t ulBitsToClearOnEntry,
 uint32_t ulBitsToClearOnExit,
 uint32_t *pulNotificationValue,
 TickType_t xTicksToWait );

11. Task Notifications Used in
Peripheral Device Drivers: UART
Example
UART Interrupt
Send Task
Interrupt 1 Interrupt N

12. Task Notifications Used Directly Within an
Application